#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;

int singleNumber(vector<int>& nums) {
    sort(nums.begin(), nums.end());
    int slow = 0;
    int fast = 2;
    int sz = nums.size();
    while (fast < sz && nums[slow] == nums[fast])
    {
        slow += 3;
        fast += 3;
    }
    return nums[slow];
}
int main()
{
    vector<int> v;
    v.push_back(2);
    v.push_back(2);
    v.push_back(3);
    v.push_back(2);
    singleNumber(v);
    return 0;
}